Simplified analysis and evaluation of drive characteristics of fully‐pitched winding reluctance motors

Compared to the conventional SRM, fully‐pitched winding reluctance motors have a higher salient ratio for given motor dimensions. In addition, since the generated torque of the motor is determined as the product of the rate of change of mutual inductance with respect to a rotor position and winding current amplitude of the corresponding two phases, the motor is suitable for the bipolar current drives. Accordingly, the conventional general‐purpose inverter drive of the fully‐pitched winding reluctance motor is possible. In this case, the optimum lead angles of voltage play an important role in obtaining the maximum torque and maximum torque/current ratio operations. In this paper, a scheme for determining the optimum angles of voltage without any measurement, and a method for evaluating the drive characteristics in the design stage are proposed by a combination of simple magnetic and electrical analysis. The effectiveness of the proposed analytical scheme is verified by an experiment using a 400‐W prototype fully‐pitched winding reluctance motor. © 2000 Scripta Technica, Electr Eng Jpn 134(1): 45–52, 2001     

Effect of Tensile Stress on Hall Coefficients of Nickel-Base Superalloys

This paper reports on Hall Effect measurements on nickel-base superalloys and their stress dependency. The work is motivated by the desire to develop a nondestructive method of characterizing the near-surface protective residual stress in metals. Our approach is based on the assumption that the Hall coefficient deviates under the stress. It is anticipated that stress measurements based on the Hall Effect are less contaminated by cold work and other effects than conductivity-based measurements such as eddy current. The paper focuses on the two superalloys, Inconel 718 and Inconel 600. The challenge is that Hall coefficients are small in metals, and the stress-induced changes are even smaller. To measure the small effect, the lock-in technique was used, with AC injected current and AC magnetic field. It was found that the Hall coefficients indeed vary proportionally to the stress. The proportionality coefficients are significantly larger than what are estimated from the volumetric effect in a free carrier gas model. The temperature and injected current dependences of the Hall coefficients were also measured, while no dependence on the magnetic flux density was observed.     

Remarkable difference of phase transition behaviors between Langmuir monolayers and aqueous bilayer vesicles of oligopeptide-carrying lipids

In this research, we synthesized six kinds of oligopeptide-carrying lipids which possessing glycine, diglycine, triglycine, alanine, dialanine, and trialanine residues (see Figure 1 for their formulae), and systematically investigated their phase transition behaviors both at the air-water interface and in aqueous bilayer vesicles. pi-A Isotherms of Langmuir monolayers of these lipids were measured at the air-water interfaces under varied temperature conditions and were analyzed based on compressibility of the monolayers. Above the specific temperature, the transition pressure from its expanded phase to condensed phase is not distinguishable with the collapse pressure of the monolayer, i.e., the monolayer collapses directly from the expanded phase without forming the condensed phase. This temperature was defined as the phase transition temperature of the monolayer, which was compared with the phase transition temperature of the corresponding bilayer vesicle in water. The phase transition temperatures of the oligoglycine-carrying lipids and oligoalanine-carrying lipids are significantly different at the air-water interface, while the corresponding difference is not obvious in their aqueous bilayer vesicles. Consideration based on molecular structures suggests necessity of the water mediation for effective formation of hydrogen bonding between the oligopeptide residues directly connected to dialkyl chains. Therefore, the differences in water accessibility to the films may cause the difference of the phase transition behaviors of the oligopeptide-carrying lipids between the Langmuir monolayers and the aqueous bilayer vesicles. Although the proposed mechanism is not fully supported by experimental evidences, the data presented here clearly demonstrated the presence of significant difference of the phase transition properties between the Langmuir monolayers at the air-water interface and aqueous bilayer vesicles of the oligopeptide-carrying lipids.     

Dramatic effect of dispersed carbon nanotubes on the mechanical and electroconductive properties of polymers derived from ionic liquids

Free-radical polymerization of an imidazolium ion-based ionic liquid bearing a methacrylate group, gelling with single-walled carbon nanotubes (SWNTs), allows fabrication of a mechanically reinforced, electroconductive soft material (bucky plastic). A film sample of this material displays an excellent conductivity of 1 S cm(-1) and a 120-fold enhancement of the Young's modulus at a 7 wt % content of SWNTs. The conductivity is temperature-dependent in the range 5-300 K, suggesting that the conductive process involves carrier hopping. Scanning electron and atomic force micrographs of a bucky plastic film display the presence of crosslinked networks consisting of finely dispersed SWNTs. Such nanotube networks, developed in the polymer matrix, likely suppress slipping of entrapped polymer molecules via a strong interfacial interaction and also facilitate intertubular carrier transport. Although a bucky plastic derived from a vinylimidazolium ion-based ionic liquid monomer shows a comparable conductivity to that of the methacrylate version, the film is brittle irrespective of the presence or absence of SWNTs.     

Sensorless control of SRM using magnetizing curves

Among various variable speed drives, switched reluctance motors (SRMs) have been found to be competitive with traditional ac and dc motors because of their simple construction and drive electronics. However, the necessity of using a shaft‐mounted position sensor is one of the drawbacks of the SRM from the standpoint of cost, size, and reliability. Position sensorless SRM drives are expected to solve these problems. This paper presents a method of position sensorless control based on a simple fuzzy model of nonlinear position‐dependent magnetizing curves. The sensors needed for the drive are one voltage sensor and one current sensor. Experimental studies using a 1.5‐kW, 5400‐rpm SRM with a 6/4 tooth configuration show that the maximum error of rotor position estimation is less than three mechanical degrees in the 1:20 speed range under any load conditions. © 2001 Scripta Technica, Electr Eng Jpn, 135(2): 60–68, 2001     

Better governance for integrated management of the Lake Biwa—Yodo River Basin

The present study discusses the efforts of the Union of Kansai Governments to resolve serious issues in the Lake Biwa—Yodo River Basin in Japan. It identifies many of the issues related to the basin on a ‘no man's land’ mindset of today's governmental framework, which has constrained both the will and the approach to remedy the associated problems. It also highlights better governance that not only encourages individual efforts, but also promotes collaboration and cooperation among the major stakeholders in the area, as important to developing acceptable solutions to relevant issues. The present study also recognizes objective scientific evidence as an effective driver for improving governance, being the basis for making informed decisions and highlighting the use of appropriate indicators to evaluate the conditions characterizing a specific location or the basin as a whole. The present study also describes the Union of Kansai Governments as a behind‐the‐scenes coordinator that gathers knowledge and intelligence on the basin, and works to integrate policies by getting basin stakeholders to gradually improve governance by repeating a cycle of: (a) recognizing the current situation; (b) identifying relevant issues to be addressed; (c) establishing a framework and policy for collaboration and corporation; and (d) taking necessary actions. To this end, the present study discusses the studies and efforts of the Union of Kansai Governments to develop and implement integrated management of this important interlinked lake–river water system in Japan.     

Dislocation and point-force-based approach to the special Green's Function BEM for elliptic hole and crack problems in two dimensions

In this paper we give the theoretical foundation for a dislocation and point-force-based approach to the special Green's function boundary element method and formulate, as an example, the special Green's function boundary element method for elliptic hole and crack problems. The crack is treated as a particular case of the elliptic hole. We adopt a physical interpretation of Somigliana's identity and formulate the boundary element method in terms of distributions of point forces and dislocation dipoles in the infinite domain with an elliptic hole. There is no need to model the hole by the boundary elements since the traction free boundary condition there for the point force and the dislocation dipole is automatically satisfied. The Green's functions are derived following the Muskhelishvili complex variable formalism and the boundary element method is formulated using complex variables. All the boundary integrals, including the formula for the stress intensity factor for the crack, are evaluated analytically to give a simple yet accurate special Green's function boundary element method. The numerical results obtained for the stress concentration and intensity factors are extremely accurate. © 1997 John Wiley & Sons, Ltd.     

Experience of superheater tubes in municipal waste incineration plant

Two years after the start of operations at the Tokachi Association for Municipal Waste Disposal and Treatment Services municipal waste incineration plant (name: Kuririn Center), which generates 400°C steam, an investigation of the plant's superheater tubes was conducted. The investigation consisted primarily of analyzing ash deposits, measuring tube wall thickness loss and observing tube sections after removal. The concentration of Cl in the deposited ash was found to increase as the temperature of the gas rose, and the amount of deposited ash tended to increase as the temperature of the gas rose. Tube damage consisted primarily of a uniform loss in thickness. Intergranular corrosion and other local corrosion was not observed. The results of thickness‐loss measurements showed that, after approximately two years in operation, tubes (SUS310) lost a maximum of 0.45 mm in thickness due to high‐temperature corrosion in locations where the steam temperature reached 400°C. Superheater tubes were also apparently damaged from the effects of a soot blower, resulting in an observed maximum loss of 0.9 mm thickness after approximately two years. Furthermore, the rate of thickness loss tended to increase after one year had passed.     

Radially and azimuthally dependent resonance self-shielding treatment for general multi-region geometry based on a unified theory

A unified resonance self-shielding method, which can treat general sub-divided fuel regions, is developed for lattice physics calculations in reactor physics field. In a past study, a hybrid resonance treatment has been developed by theoretically integrating equivalence theory and ultra-fine-group slowing-down calculation. It can be applied to a wide range of neutron spectrum conditions including low moderator density ranges in severe accident states, as long as each fuel region is not sub-divided. In order to extend the method for radially and azimuthally sub-divided multi-region geometry, a new resonance treatment is established by incorporating the essence of sub-group method. The present method is composed of two-step flux calculation, i.e. ‘coarse geometry + fine energy’ (first step) and ‘fine geometry + coarse energy’ (second step) calculations. The first step corresponds to a hybrid model of the equivalence theory and the ultra-fine-group calculation, and the second step corresponds to the sub-group method. From the verification results, effective cross-sections by the new method show good agreement with the continuous energy Monte-Carlo results for various multi-region geometries including non-uniform fuel compositions and temperature distributions. The present method can accurately generate effective cross-sections with short computation time in general lattice physics calculations.     

Ultra-fine-group resonance treatment using equivalent Dancoff-factor cell model in lattice physics code GALAXY

In order to achieve highly accurate resonance calculations with short computation time , a new ultra-fine-group resonance calculation method is developed. The ultra-fine-group method has a limitation in practical design applications of large and complicated geometries in fuel assembly level due to its long computation time. Therefore, we developed an enhanced one-dimensional (1D) cylindrical pin-cell model to achieve both high calculation accuracy and short computation time. In the enhanced 1D cylindrical pin-cell modeling, moderator radius is adjusted to preserve each fuel pellet's Dancoff factor obtained in the exact 2D fuel lattice arrangement. We call this model the ‘equivalent Dancoff-factor’ cell model. This model can accurately consider heterogeneity effects in PWR fuel assemblies and can represent effective cross sections obtained by the ultra-fine-group calculations in the complicated 2D square lattice arrangements. The present method is implemented with Mitsubishi Heavy Industries, Ltd. lattice physics code GALAXY. From the comparisons of neutron multiplication factors and pin power distributions between GALAXY and a continuous-energy Monte Carlo code, applicability of the present method to lattice physics calculations is confirmed. Application of GALAXY with the present method achieves high accuracy with short computation time in normal operations and accident conditions including low moderator density conditions.